For a long time, people have been committed to the research and development of new energy storage systems. Among them, lithium sulfur secondary batteries are considered the most attractive battery system. Sulfur has the highest theoretical specific energy (2800 Wh/kg) and theoretical specific capacity (1675 Ah/kg) compared to other battery systems.
However, lithium sulfur batteries generate polysulfides during charge-discharge cycles. The polysulfides dissolve in organic electrolytes, resulting in irreversible loss of active material and decay of capacity. Moreover, with the insertion and extraction of lithium ions during the charge-discharge cycle, the sulfur cathode electrode has a volumetric expansion and contraction. As cycling number increases, the cathode electrode structure collapses and the cathode electrode material spalls, causing a rapid decay of the capacity.
Experiments have shown that a commonly used oily binder such as polyvinylidene fluoride (PVDF) has a deteriorated cycling performance for lithium sulfur batteries. An aqueous binder such as polyacrylic acid or polyacrylate is used in the lithium-sulfur battery system. However, during the manufacturing of the electrode, the cathode active material, such as sulfur, is mixed with the conducting agent and the binder in a solvent to form an electrode slurry, which is coated on the surface of the current collector and then dried to remove the solvent. For oily binders, volatile organic solvents can be used to make electrode slurries that are easier to dry. For aqueous binder, a relatively long time is needed to thoroughly dry water in the slurry at a relatively low temperature, during which the cathode active material may be oxidized.